1. Field of Invention
The present invention relates to a method of electric circuit layout, and particularly to automatic enlarging width of bend portion, and computer readable recording medium for storing program with aforesaid method.
2. Prior Art
In electric circuit layout, it is needed to implement a plurality of longitudinal and latitudinal circuit lines (leads) to obtain electric connection between the devices. Generally, aforesaid longitudinal and latitudinal electric lines interconnect by 90 degree angle. In considering on some electric characteristics or electric circuit area, a bend portion is usually needed to be implemented in the electric circuit sometimes. For example, in an integrated circuit, a gate electrode of transistor is designed to be a circuit line with 45 degree bending for saving electric circuit area.
FIG. 1 is a top view, schematically illustrating a conventional transistor which has a gate electrode with bend portion by 45 degrees. Referring to FIG. 1, the gate line 120 of the transistor 100 is designed to have 45-degree bend portion 121, then the source contact window 110 and the drain contact window 130 are respectively implemented at two sides of the bend portion 121. Therefore, the area of the transistor 120 can be significantly reduced.
However, during forming the gate line 120 with a line width W0, it is often that the edge of the bend portion 121 is over etched due to processing effect. As a result, the line width of the bend portion 121 is reduced to W1. If the line width W0 is large enough, the influence of over etching is limited (W1 is approximate to W0), thus, characteristic of the transistor 100 (ratio of length to width of the channel) has no change almost. But, when more an advanced process (for example, process with line width smaller than 0.25 microns) is used to fabricate the transistor 100, because the line width W0 is thinner, the difference between W0 and W1 cannot be ignored. In order to ensure the ratio of length to width for the channel of the designed transistor 100, a conventional method is to pre-enlarge the line width of the bend portion 121 to W2.
In the present practice, after circuit layout is finished by using the tool of electronic design automation, the 45 degree bend portion is manually searched one by one, and then the electronic design automation tools are manually manipulated to pull each edge of the 45 degree bend portion outward to be wider. Hence, in order to enlarge the line width of the 45 degree bend portion, often, much time is spent on circuit layout modification in layout engineering.